This study was aimed at examining the relationship between the horizontal upper eyelid peak position (Δpeak-pupil) and the difference between the medial and lateral canthal heights (Δcanthi) in Japanese individuals. Images of the left eyelid of 71 participants without eyelid disease were acquired with a camera with a slit-lamp microscope. Multivariate linear regression analysis was performed to determine the influence of age, sex, distance from the pupil center to the upper eyelid margin (margin reflex distance-1), Δcanthi, and palpebral fissure width on Δpeak-pupil. In addition, Δpeak-pupil distribution in participants with Δcanthi <3 (Group A), 3 to 6 (Group B), and >6 mm (Group C) was calculated as the average±2x the standard deviation. The mean Δpeak-pupil was 1.12 ± 1.29 mm (range: -1.44 to 6.12) and the mean Δcanthi was 4.50 ± 1.71 mm (1.02-7.96). Δcanthi was a significant determinant factor of Δpeak-pupil (P < 0.0001), whereas age (P = 0.62), sex (P = 0.88), margin reflex distance-1 (P = 0.29), and the horizontal palpebral fissure width (P = 0.65) were not related to Δpeak-pupil. The normal Δpeak-pupil ranges were -1.47 to 1.52, -0.95 to 3.22, and -0.84 to 4.73 mm in Groups A, B, and C, respectively. There was a statistically significant difference between the Group A and B ranges and between the Group A and C ranges (Kruskal-Wallis test, P < 0.01). It was concluded that the normal eyelid peak position differs according to medial-to-lateral canthal positional difference. This finding may help intraoperative determination of the upper eyelid peak position in blepharoptosis surgery.